FIG. 14 is a cross-sectional view schematically showing configuration of a conventional type of disk unit which is mounted on a servo track writer. In FIG. 14, designated at the reference numeral 41 is a base, at 42 a disk, at 43 a spindle motor, at 44 a head actuator mounting the head thereon, at 45 a voice coil motor, at 51 a stage, at 52 a clock head, at 53 an actuator for a pin pick, and at 54 a pin pick. It should be noted that a magnetic disk is used for the disk 42 as one example herein.
As shown in FIG. 14, when a disk unit is a type having a base cover, for example, almost all components of the disk unit excluding a cover (not shown) and a printed board (not shown) are assembled on the base 41, and the assembled components are fixed to the stage 51 of the servo track writer.
With those steps, the clock head 52 dedicated to writing/reading of a reference clock is loaded on one face of the disk 42 (e.g. on the top surface of the uppermost disk as shown in the figure), and on the other hand the actuator 53 for a pip pick for the servo track writer, which is a different body from the head actuator 44 for the disk unit itself, presses down a movable section of the head actuator 44 for the disk unit itself via the pin pick 54. For this reason, operations for positioning and moving the movable section of the head actuator 44 are executed for each track, and an operation for writing data in a servo track on a disk is executed according to the operations.
Recently, some disk units do not employ a self-servo data write system for writing servo data with a combination of a disk laminated body and a head, but employ an embedded servo system for writing servo data in the state of spindle assembly where the disks are laminated on the spindle using the head dedicated to writing data in a servo track on a disk and the head actuator.
In the conventional type of system, however, when it is required to write servo data in the entire data face like in the embedded servo system, if displacement of the head is large, displacement occurs in the radial direction of the disk as well as in the direction of perimeter thereof, which may lower performance as a disk unit. Therefore, under the current tendency for minimization of disk units, as shown in FIG. 14, it is desirable to write servo data in a state where combination of the spindle motor 43 with the head actuator 44 is maintained.
In the conventional type of servo track write system, an operation for writing data in a servo track on a disk is executed using a servo head (data head in the embedded servo system) mounted on the disk unit, so that a position of a stopper restricting a movable range of the head actuator for each disk unit may not be uniformed according to differences in dimensional precision of the components or dimensional precision in assembly.
Assuming non-uniformity in a stopper position as described above, generally a track pitch is previously set to a narrow width so that data will be written in all cylinders previously specified even if there is any dimensional non-uniformity within an allowable range of common difference in a stopper position.
Description is made herein for the conventional type of disk with reference to FIG. 15 and FIGS. 16A to 16C. FIG. 15 is a view showing an example of zone layout on a disk, and FIGS. 16A to 16C are views showing an arrangement of servo data on a disk shown in FIG. 15 in the radial direction thereof.
FIG. 15 shows in comparison zone layouts ZL1, ZL2, and ZL3 on three types of disk units each with data written in a servo track thereon and also each assembled with a different stopper space. Comparing the sizes of the zone layouts ZL1, ZL2 and ZL3 to each other by aligning the outer-side stopper positions OSP at the left side edge (in the figure), inner-side stopper positions ISP are away from the outer-side stopper position OSP in the ascending order of ISP2, ISP1, and ISP3. From the difference among the stopper spaces, a relation among the sizes of the zone layouts ZL1, ZL2, and ZL3 is ZL2 (narrowest stopper space)&lt;ZL1 (intermediate stopper space)&lt;ZL3 (widest stopper space).
However, the operation for writing data in a servo track on a disk requires, as already described, a condition in which data is written in all the prespecified number of cylinders on the disk regardless of the stopper space, so that the same number of data tracks are provided on each of the zone layouts ZL1, ZL2, and ZL3 with the same track pitch. Namely, each of the zone layouts ZL1, ZL2 and ZL3 has a data zone DZ with the same size as shown in FIG. 15.
If there occurs any displacement in the stopper space from the outer side edge as a reference, outer guard zones OGZ each having the same size are provided in the outer side of the zone layouts ZL1, ZL2 and ZL3, and also inner guard zones IGZ1, IGZ2 and IGZ3 each having a difference size according to the difference in the stopper space are provided in the inner side. A relation among the sizes is as indicated by the following relational expression: IGZ2&lt;IGZ1&lt;IGZ3.
Practically, the relation among the zone layouts ZL1, ZL2 and ZL3 is as shown in FIG. 16A, FIG. 16B, and FIG. 16C respectively. A spare zone outside the movable range of the actuator in the inner side exists in a space, in the radial direction of the disk, from the circuit up to the inner guard zone. Assuming that the outer side stopper position OSP is fixed, this spare zone and the inner guard zone have a relation in which the inner guard zone is, when the spare zone is widened, in turn narrower.
Namely, to make description simple, considering each inner guard zone for each zone layout with reference to the spare zone of the zone layout ZL1 as a reference, the zone layout ZL2 has a wider spare zone and has in turn a narrower inner guard zone IGZ2, while the zone layout ZL3 has a narrower spare zone and has in turn a wider inner guard zone IGZ3.
In the servo track write method according to the example based on the conventional technology, a data zone and a track pitch are specified so that all of a prespecified number of cylinders can be obtained on a disk even when a stopper space becomes the narrowest due to nonuniformity of dimensions thereof, and for this reason, even when the stopper space becomes larger as that in the disk shown in FIG. 16C, it only makes an inner guard zone wider, namely it expands an area in which data is not written, which does not give any influence requirement that the operation for writing data in a servo track on a disk is executed in a required narrowest data zone according to a required narrowest possible track pitch.
In recent years, in association with increasing demands for larger capacity of a disk unit, a recording density in a disk unit becomes increasingly higher, and as a result, the technology is approaching limits in memory capacity as well as in capability of securely recording data.